“Dead letter” has a figurative legal/administrative sense for a rule or agreement that has become ineffective and a distinct postal sense for mail that cannot be delivered or returned. This guide keeps those senses separate and does not assert unsupported origin chronology.
ReviewedEvidence1 sourceSectionPhrases & Idioms
Quick answer
A “dead letter” can mean a law or agreement that is formally still present but no longer effective; it also has a separate literal postal sense for undeliverable mail.
Key details
Canonical Formdead letter
Core Meaninga law, rule, agreement, or similar instrument that exists formally but is no longer effective; also an undeliverable and unreturnable postal item
Further guidance
History Boundary
Current dictionary-supported meaning is published without claiming an exact inventor, coinage date, or absolute first use.
Meaning
a law, rule, agreement, or similar instrument that exists formally but is no longer effective; also an undeliverable and unreturnable postal item
Usage Boundary
Do not confuse the figurative ineffective-rule sense with the literal postal sense; context determines which meaning is intended.
Sources and evidence
Sources are shown with the role they play in this guide. Historical or style-sensitive claims are kept within the evidence boundary described above.
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“A slap on the wrist” is an informal idiom for a mild warning or punishment. It is usually figurative and can carry the implication that the consequence was light compared with what was expected or deserved. This guide does not attach an unsupported origin chronology.
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Use “acid test” for a test or standard that reveals whether something really has the claimed quality, value, or success. The guide stays with current documented meaning and does not assert unsupported origin chronology.
“Actions speak louder than words” emphasizes conduct over verbal claims: actions can reveal intentions and feelings more clearly than words alone. This guide publishes the current saying and meaning without adding an unsupported exact-origin claim.
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